Spreading ridges along some of the oceans cordilleras are zones of huge quantities of thermal energy released by means of deep see water circulation that penetrates fractures on the upper ocean crust. Hot magma is not very deep in these spreading zones. This thermal energy can be mined if an appropriate procedure is available. The thermal energy is produced by the infiltration of seawater through faults, fractures and porous zones in the upper oceanic crust to depths where the ascending magma has high temperatures. That water returns to the sea forming thermal vents with water temperatures up to 450° C. or more. Although there are also vents with low temperature.
The ascending water speed of the vent may vary from low values to values as one meter per second or more. This ascending water tends to be very acidic.
U.S. application Ser. No. 12/718,546, filed Mar. 5, 2010 (Alberto Sarria), discloses a method for using concentric tubes placed deep underground to heat water or other liquids by geothermal energy, and generating electric power and/or desalinized seawater.
U.S. Pat. No. 8,001,784 (Marshall) discloses a system that recovers superheated fluids from deep-ocean hydrothermal vents and allows those fluids to be utilized as a thermal energy source. The system is configured to direct a flow of superheated deep-ocean hydrothermal fluid to the surface for use in generating electricity or desalinating water.
A thermal vent may be considered a special kind of small volcano lying on the sea bottom. There are also full volcanoes on the sea bottom. Thermal vents form and persist for years but may be destroyed from time to time. The location of a thermal vent depends on the hot magma position, which means that they are not located all along the spreading ridges in the oceans, and also means that the formation of new vents or the improvement of those that are active may be stimulated by artificial procedures similar to those used in the EGS geothermal mining.
The thermal vents may be located at depths which vary from a few hundred to over three thousand meters. There are spreading ridges zones in the middle of the oceans and some are located more or less near the cost. That is the case in Juan de Fuca Ridge, near the coasts of Oregon and Washington states in the United States, in the Red Sea, near the coasts of Turkey and Italy and in some other parts of the world.
The chemical composition of the water flowing upward from the thermal vents is corrosive because as water penetrates through the fissures it dissolves some acid components of the rock. This corrosive characteristic combined with the high water temperature has to be taken into consideration in any procedure in the mining of the thermal energy of the vents hot water. Also, those special conditions are the origin of very particular species of fauna and flora.
The hydrocarbon industry has developed an important expertise in working at the sea bottom. Many studies by governmental agencies and special research programs have been done to locate and identify the thermal, hydraulic and temperature characteristics of the deep ocean. The fracturing of rocks by injecting high-pressure water is a common procedure widely used in continental areas as well as sea bottom hydrocarbon reservoirs.
Most of the thermal vents and promising spreading ridges are still to be located or evaluated from the point of view of chemical and physical characteristics of the water ascending from the vent. Also, the possibility to improve the thermal characteristics of some vents and the possibility to create new vents by artificial procedures like rock fracturing have yet to be studied.